This invention relates generally to electrophotographic reproduction machines, and more particularly, concerns an air duct seal assembly suitable for low pressure air ducts that are intended to be disconnected and reconnected, such as those found in printers and copiers.
Generally, in the process of electrophotographic reproduction an image of an original document to be copied or printed is placed onto the surface of a photoconductive member (or photoreceptor) either by illuminating the original document, which is projected upon the photoconductive member to produce a latent electrostatic image corresponding to the original document, or by placing the image onto the photoreceptor by electronic means. The latent electrostatic image is developed by means of fusible particles to produce a visible toner image that is transferred to a substrate, such as a piece of paper. The unfused toner image may be fixed to the substrate by means of heat and pressure by pressing the substrate through the nip of a pair of rollers, at least one of which is heated.
It is essential to the maintenance of copy quality and reliability that the machine environment be controlled. For example, ozone emission is tightly regulated for health and safety reasons, and dirt and toner dust has been shown to be one of the most significant contributors to machine failures and service actions. In addition, paper debris, such as fibers and dust fillers, contribute significantly to failures of machines. For instance, debris in the paper path fouls sensors, solenoids, and frictional materials; fillers foul fuser oils; and fibers ruin photoreceptor belts. Thus, low pressure air systems (i.e., less that one inch of water pressure) are often used in electrophotographic reproduction machines as a means of controlling the machine environment. In smaller machines a single blower will generally purge and cool the entire machine with ambient air. In larger machines, several blowers are generally required to serve as subsystems by the addition or removal of air. In these machines, duct work is often required to direct the air since it is not always practical to place an air handling device directly at the point of application.
Further, with the advent of high speed reproduction machines, wherein copiers or printers can produce at a rate in excess of several thousand copies per hour, the need for sheet handling systems to, for example, feed paper or other media through various process stations in a rapid succession in a reliable and dependable manner in order to utilize the full capabilities of the reproduction machine is apparent. These sheet handling systems must operate flawlessly to virtually eliminate risk of damaging the recording sheets and generate minimum machine shutdowns due to misfeeds or multifeeds. It is in the initial separation of the individual sheets from the media stack where the greatest number of problems occur which, in some cases, can be due to curl up curl and down curl in sheets which generally occur randomly in the document stack. Accordingly, these machines can require a separate low pressure air system featuring duct work to fluff the paper.
An important concern in such low pressure air systems is maintaining an air tight seal in the duct work. In some instances, it can be necessary to have portions of the air duct that repeatedly disconnect and reconnect, such as when a drawer (or door) is opened and closed. That is, an air duct piece may be mounted somewhere on the machine body and form a connection with another air duct piece mounted on a drawer when the drawer is closed to duct air through the machine. In this situation, it is necessary to be able to maintain a tight seal each time the two air duct pieces are disconnected and subsequently reconnected by opening and closing the drawer.
It is known to provide mounting flanges extending radially outwardly at the ends of the two air duct pieces that are to be connected. One of the flanges can have a piece of compressible, open-ell foam attached to its planar end face for engagement with the planar end face of the other flange. Therefore, when the drawer is closed and the two air duct pieces are reconnected, the foam can provide a seal. However, this connection is not without problems. For instance, the foam used in this type of connection has a tendency to permanently deform and not seal properly after repeated use. Also, the use of flanges on the connecting ends of the air duct portions can give the seal a high profile, which is not desirable in tight spaces where space is a prime consideration. Furthermore, this type of connection has low penetration latitude, providing a short sealing surface in the plane perpendicular to the axis of the duct. Simply increasing the length of foam in an attempt to increase the penetration latitude will not work because the foam becomes increasingly unstable due to stack-up tolerances as its length is increased.
It is also known to use an O-ring to seal smaller air ducts, i.e., those less than 5 millimeters in diameter. However, an O-ring alone will not work when the air duct has a diameter greater than 5 millimeters. This is because of the high friction caused by the increased diameter of the O-ring.
Therefore, although the above-described seals have been successful to some extent, an improvement is still needed.
In accordance with one aspect of the present invention, an improved low pressure air duct seal assembly for use with air ducts that are intended to be disconnected and reconnected is disclosed, which is space efficient, creates an air tight, stable seal, has high penetration latitude, and provides for low friction reconnection. This improved air duct seal assembly features the use of a thin layer of heat shrink tubing over a compressible O-ring, which is disposed in a groove around the outside of one of the air duct pieces to be connected, thus creating a low friction sealing surface. This duct piece is then inserted into a coupling with a corresponding sealing surface and connects with the receiving air duct piece. The purpose of the compressible O-ring is to make the seal compliant and to allow for variations in part diameter. The heat shrink tubing is used to hold in the O-ring and to reduce the insertion force by reducing the friction between it and the sealing surface on the receiving duct piece.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.